32597-32-3Relevant academic research and scientific papers
The ultraviolet photochemistry of diacetylene: Direct detection of primary products of the metastable C4H2* + C4H2 reaction
Bandy, Ralph E.,Lakshminarayan, Chitra,Frost, Rex K.,Zwier, Timothy S.
, p. 5362 - 5374 (1993)
The products of diacetylene's ultraviolet photochemistry over the 245-220 nm region are directly determined for the first time.At these wavelengths, the photochemistry is thought to proceed from a metastable excited state of C4H2 rather than by direct photolysis.The experimental method employs a small reaction tube attached to a pulsed nozzle.C4H2 is excited within the reaction tube where collisions of C4H2* with C4H2 form products which are subsequently ionized by vacuum ultraviolet radiation (118 nm) in the ion source of a time-of-flight mass spectrometer.The C4H2* + C4H2 reaction produces H6H2 (+C2H2), C8H2 (+2H,H2), and C8H3 (+H), all in good yield.An extensive set of experiments is carried out to ensure that the products observed are initial products formed by single-photon excitation of gas phase C4H2.Under certain conditions, secondary products formed by subsequenct reaction of the initially formed products with C4H2 are also observed.These are dominated by C10H3 and C12H3.Thermochemical arguments are made which point to C8H3 + C4H2 as the source of these secondary products.Collisional deactivation of C4H2* from its initially excited energy (ca. 120 kcal/mol above the ground state) to the lower levels of the metastable state (ca. 74 kcal/mol) is important in determining the relative amounts of C8H2 and C8H3 products.In cases where C4H2* undergoes extensive deactivation prior to reaction, C8H3 + H products dominate.When collisional deactivation is minimized, much of the C8H3 products are formed with enough energy to subsequently dissociate further to form C8H2 + 2H.Mechanisms are postulated for the observed reactions and some suggestions for further work to assess the importance of these reactions in planetary atmospheres are given.
Polyynes and cyanopolyynes synthesis from the submerged electric arc: About the role played by the electrodes and solvents in polyynes formation
Cataldo, Franco
, p. 4265 - 4274 (2007/10/03)
The products of the electric arc between graphite electrodes have been investigated by high performance liquid chromatography-diode-array detector (HPLC-DAD) analysis in various media: distilled water, liquid nitrogen, methanol, ethanol, n-hexane and benzene. In distilled water, hydrogen capped polyynes H-(CC)n-H were the unique products demonstrating that carbon is supplied by the graphite electrodes while hydrogen is supplied by the solvent plasmalysis (in this case water plasmalysis). Arcing graphite electrodes in liquid nitrogen produces cyanopolyynes: NC-(CC)n-CN demonstrating that in this case the end groups of the polyyne chains are supplied by molecular nitrogen plasmalysis caused by the electric arc. Graphite arcing in methanol and ethanol produces very clean solutions (by-products negligible or absent) of hydrogen-capped polyynes with C8H2 as the main product accounting for more than 70 mol percent of the total polyyne concentration. By replacing graphite electrodes with titanium electrodes in methanol or in ethanol, polyynes are not formed at all; only trace amounts of polycyclic aromatic hydrocarbons (PAHs) were detected. When arcing with graphite electrodes is conducted in n-hexane or in benzene, polyyne formation is accompanied by a significant production of PAH, especially in benzene. These results have been rationalized in terms of carbonization or coking tendency of a given solvent. The effect of using titanium electrodes in place of graphite electrodes has been investigated also in n-hexane and in benzene as well as the effects of very high electric current intensity employed to ignite and sustain the submerged electric arc.
